Evaluating the Hazards of Radiation and its Sources

Procedure

Time: Approximately 50 minutes

Materials:Prerequisites:Internet access for all students plus (optional) report forms for students to complete. Some instructors may prefer students to assemble reports individually providing greater challenge to determining the appropriate information.

Implementation: This RWLO should be used in the
classroom during a study of radioactivity, types of radiation and nuclear fission. It could also be used as a homework assignment since all the resources are available online. Familiarity with the concept of ionizing radiation is an advantage.

Students will first familiarize themselves with the units of measurement of radioactivity and radiation exposure and be able to convert between these units. They will be able to tabulate the physiological consequences associated with increasing levels of exposure. Using an online radiation exposure "calculator," students will then be able to calculate their own annual radiation dose from all sources and be able to identify the most significant sources of radiation exposure.

The online calculator serves as a primary data source for the exposure levels to various forms of radiation. The source for these data are the National Council on Radiation Protection and Measurements Reports #92-#95, and #100. These reports cost $40 each and so are not readily available in printed form to students. The EPA online calculator provides a unique and compelling way to determine exposure levels to all forms of radiation and enables sensitivity to different types of behaviour or environment to be evaluated.

The second activity that makes unique and compelling use of the internet is to formulate a question within class and "ask the expert." The Health Physics Society website offers this feature. Students should study the FAQs to see what questions have already been asked and then formulate one about a radiation issue and submit it.

Students would then be prepared to engage in a discussion of the real dangers of nuclear power and its role as an alternative to fossil fuels.

Steps:

Step 1.

Instructor should be familiar with units of radiation and exposure. Students will search for and discover these using the internet resources suggested in the materials content. There are three types of measurement, each of which has two units of different magnitude. The table below is what the students will complete as the first part of the exercise.

Quantity measured

Unit name

Dimensions

Decay events (Radioactivity)

Becquerel (Bq)

Amount sample undergoes 1 decay/second

Decay events (Radioactivity)

Curie (Ci)

Amount sample undergoes 3.7 x 1010 decay/second

Radiation exposure (Energy absorbed per kilogram tissue)

Gray (Gy)

1 Gy = 1 J/kg tissue

Radiation exposure (Energy absorbed per kilogram tissue)

Rad

1 rad = 0.01 Gy

Equivalent radiation dose

Sievert (Sv)

1 Sv = 1 J/kg

Equivalent radiation dose

Rem

1 rem = 0.01 Sv

It is important to note that although energy absorption and tissue damage have nominally the same units, they do not measure the same thing. Energy absorbed is converted to tissue damage by multiplying energy absorbed by a factor called
relative biological effectiveness (RBE). This depends on the type of radiation and usually has a value between 1 and 10. Students will be asked to examine relationships between the units and perform conversions between units.

Step 2.

The next step is to construct a table of comparing levels of exposure to physiological effects. A template may be used for this. The outcome should look something like the following:

These exposure levels can be compared with the EPA recommended annual exposure level of 100 mrem.

Step 3.

The next step is to use the exposure calculator at the EPA website to calculate individual annual exposure to all types of radiation. This doesn't take very long and students could be encouraged to explore variables such as geographical location, height, use of air travel and so on. After completing the exposure calculation, students can be asked to identify the most important sources of natural and manmade radiation.

Step 4.

In this activity the class will "ask the expert" a question about some aspect of radiation. The Health Physics Society website offers an online "ask the expert" feature. The class should study the existing FAQs at the website to see what questions have already been asked and then formulate one about a radiation issue and submit it.

Step 5. (Optional)

This exercise can be taken further in a discussion of how students view the dangers of nuclear power generation in the light of this radiation exposure calculation. This discussion can be extended to include the dangers posed by other energy sources such as fossil fuels, biomass, solar energy, wind power and so on. This could take the form of a written assignment or a group discussion.